David Chester asks ‘Why were the groynes at Seaford not rebuilt when the beach was restored in 1987?’ (Sussex Express, January 17). Let me explain why.
In the 19th century William Collins painted a view of Seaford Beach looking west towards Newhaven.
It is devoid of groynes and there is no sea wall. The long western arm at Newhaven Harbour was built between 1878 and 1890 and the impact on the Seaford Beach was immediate and dramatic. So much so, that the government passed the Newhaven and Seaford Sea Defence Act 1898 which created a Sea Defence Commission charged with tackling the problem at Seaford.
Littoral drift, causes shingle to flow from Selsey (where the Point receded at an average rate of 9 ft per year between 1900 and 1950) and accumulate at Dungeness.
The construction of the harbour arm resulted in shingle passing along the coastline being deflected out to sea, only to come in again at the Cuckmere mouth. In addition, the wave pattern in Seaford Bay changed and this resulted in shingle on the beach east of The Buckle, to continue to flow eastwards while that west of the Buckle flowed in the opposite direction into the lee of the eastern Harbour arm.
Successive old editions of Ordnance Survey maps confirm this, showing how the tidal high water mark changed. It follows that there was no natural shingle replenishment of the Seaford beach but it is probable that the commissioners who became responsible for the defences did not fully understand this because they built groynes and a sea wall to protect the town although these were of limited value.
During the first half of the 20th century the beach levels in front of the wall continued to fall. The wall had to be underpinned – several times – collapses occurred, and as well as being a waste of resources, groyne maintenance became increasingly difficult as the tide would not recede for a sufficiently long period to permit a reasonable working time.
Under storm conditions a shingle beach is drawn down or flattened, only to slowly build up again during ensuing periods of calm weather when waves are quite gentle.
Beach material saltates under passing waves and longshore currents cause the material to travel along the coast, albeit very slowly. Groynes do not contain shingle completely and any material which is lost needs to be replaced if a beach which, incidentally, is an excellent material for absorbing wave energy, is to be maintained.
On most Sussex beaches this replacement is a natural process but for the reasons stated this does not apply to Seaford.
In 1981 the commission was disbanded and responsibility passed to the Southern Water Authority. A study of the problem was instigated and a number of potential solutions identified. Without question, the environmentally most friendly was the re-establishment of the beach. The question remained however as to what extent the new beach would stay in place. The Hydraulics Research Station was commissioned to carry out a study using one of their wave basin scale models (the size of two tennis courts) fitted with a wave making device. As a result of the research it was concluded that beach renourishment would be successful but material would continue to move towards the east and in a bad year up to 40,000 cu.m might move.
The cost of renourishing the beach with 3 million tons of shingle, building a new terminal groyne at Splash Point and other essential works, proved overwhelmingly to be the least cost option and it is important to point out that the costing took into account the discounted cost of mechanically moving shingle every year back from Splash Point towards The Buckle, in perpetuity.
The Environment Agency is correct to maintain the beach as it does. Seaford not only benefits from the defence provided, but in economic terms the town has also gained enormously since the scheme was completed in1987. Building groynes at Seaford, far from easing the problem, would exacerbate it.